I like the very light "eco" water bottles that are .75 oz for 1L.
Like Roger says, they are not nearly as strong as the heavier. But honestly, they are durable enough. Ever try to destroy one?
Just check the bottoms good, thats where leaks usually occur, at mold points. I replace them every trip , just buy a couple of new water bottles on the way and put in the pockets on my pack.
I carry 2, so I have a spare if one fails, so it doesnt worry me. I know I can make 10 miles on 1L if need to, but usually start out with 1L per 5 miles or so planned.
If I was going somewhere with NO water for days, it would be different.